The mass spectrometric behaviour of tricyclopentadienyluranium η2-iminoalkyl(cycloalkyl) derivatives; the evidence for some cyclopentadienyluranium hydride species produced by electron impact (original) (raw)
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Electron-impact mass spectrometry of methyl O-methylglucopyranosiduranamides
Carbohydrate Research, 1979
Mass-spectral fragmentation of the complete series of methyl O-methyl-cc-Dglucopyranosiduronamides has been studied. Based on 70-and 12-eV spectra, deuteration (OD and ND,) experiments, and metastable-transition and exact-mass measurements, new cleavage-reactions resulting from the simultaneous presence of hydroxyl and amido groups in the molecule have been found. The mass spectra provide information useful in the determination of number and locations of methyl groups in methyl O-methylhexopyranosiduronamides. *Dedicated to Professor Roy L. Whistler. tPart XIV of the series: Mass Spectrometry of Uranic Acid Derivatives: for Part XIII, see ref. 1.
Organic Mass Spectrometry, 1988
The electron-impact-induced mass spectra of 1,3-dioxolane (la), 1,3-dithiolane (2s) and 1,3oxatbiolane (3a) and their %methyl (lb-3b) and 2,2-dimethyl [(CH&: lc-3c or (CD,),: ld-3dI derivatives have been studied in detail to gain further insight into their ion structures and competing reaction pathways with low-resolution, highresolution, metastable and collision-induced dissociation (CID) techniques. For compounds la-ld the most significant reaction is loss of H and CH,' by a-cleavage and a subsequent formation of CHO' and C,H,O' ions. The [M-m' ions from l a and l b give a C,H,O' ion which does not have the acyl cation structure as shown by their CID spectra. In compounds 3a-3d the sulphur-containing ions predominate, the C,H,O+ now having the acyl cation structure. 1,3-Dithiolanes (2a-2d) exhibit the most complicated fragmentation patterns. Furthermore the [M-HI+ ion from 2a and-CHJ+ ion from 2b have different structures as well as the [M-a' ion from 2b and [M-CH,]' ion from 2c, as shown by their CID spectra. This can be utilized to explain why 3a-3c and 2s give principally a thiiranyl cation, whereas 2b gives a mixture of this and the thioacyl cation and 2c practically only the open-chain thioacetyl cation.
OMS, Organic mass spectrometry, 1978
The negative ion mass spectra of a series of monomeric and dimeric r)s-cyclopentadienyl transition metal carbonyls have been examined. The base peak in the case of the monomeric compounds (r)s-C,H,)V(CO)4, (qs-C,Hs)Mn(CO), and (q5-CH,C5H4)Mn(CO), arises from a reductive decarbonylation of the parent molecule-the resulting radical anion [M-CO]: is formally isoelectronic with the molecular cations [MI? observed in the positive ion mass spectra of these compounds and subsequently undergoes successive decarbonylations to the 'aromatic' cyclopentadienyl anions. For the compound (q5-C5H5)Co(CO),, however, a molecular anion was observed as the base peak which has been formulated as [(q3-C5H5)Co(CO),l7 in the light of considerations based on the rare gas rule. As expected, the dimeric molecules [($-C,HS)M(C0),], (where M = Cr or Mo) and [(q5-C,H,)Fe(C0),], (and its methyl analogue) undergo reducrioe cleaoage of their metal-metal bonds to give the anions [(q5-C,H,)M(CO),]-and [(q5-C5H5)Fe(CO),]-as the base peaks in their negative ion mass spectra. The dimeric nickel compound [(~5-C,H,)Ni(CO)],, however, reductively decarbonylates to the [M-CO]: radical anion as its predominant hawentation in the gas phase. Very low abundances of [(q5-C,H,)Fe(C0),]$ and [(q5-CH,C,HdFe(C0)& were also observed.
AM1 and electron impact mass spectrometry study of the fragmentation of 4-acyl isochroman-1,3-diones
Bulletin of the Chemical Society of Ethiopia, 2012
Recently, in electron impact mass spectrometry (EIMS), it has been found a good correlation between the fragmentation processes of coumarins and the electronic charges of the atoms of their skeleton. In this paper, the same analytical method has been applied to 4-acyl isochroman-1,3-diones, whose mass spectra had been studied earlier and described for the very first time from our laboratory. Results obtained are in good agreement with the last study.
Journal of the American Chemical Society, 1981
Gas-phase He I, He 11, and Mg Ka photoelectron spectra are reported for molecules of the type (v5-C5H5+-(CH,),)M(CO), where n = 0, 1, 5 and M = Mn, Re. The influence of methyl groups on the cyclopentadienyl ring is monitored by shifts in both core and valence ionization energies. This enables effective separation of electron density transfer (inductive) and ring-methyl orbital overlap (hyperconjugative) effects. While the shift in the ring el" ionization is found to be primarily a hyperconjugative effect, the shift in the metal valence ionizations is caused essentially entirely by a shift of electron density toward the metal atom. A greater proportion of this increased density is transferred to the carbonyls in the rhenium complexes than in the manganese complexes, indicating the greater back-bonding ability of the third-row atom. Further evidence of extensive Re-CO back-bonding is provided by the presence of vibrational fine structure on one of the predominantly metal ionizations of the rhenium complexes. This structure is the vibrational progression of the symmetric metalkarbon(C0) stretching mode. The long vibrational progression observed in this band and the frequency of the M-C stretch in the positive ion are direct evidence of considerable ?r back-bonding from the metal to the carbonyls. The observed vibrational structure in the spin-rbit split rhenium d ionizations also leads to a definitive interpretation of the pattern of metal ionizations in such complexes. The origin of the characteristic splitting of the predominantly ring el" ionization is also considered in detail. The data suggest that the carbon-carbon bond distances in the ring are distorted an average of 0.01 to 0.02 8, from fivefold symmetry when coordinated to a d6 ML3 species. This is the first indication from gas-phase spectroscopy for such distortions.
International Journal of Mass Spectrometry and Ion Processes, 1994
The gas-phase reactions of the O'-ion with ($-cyclopentadienyl)tricarbonyhnanganese(I), CpMn(COh, and (77fimethylcyclopentadienyl)tricarbonylmanganese(I), CH$pMn(CO)3, have been studied with Fourier transform ion cyclotron resonance. The main reactions are (i) proton abstraction, (ii) loss of COz, and (iii) expulsion of two or three CO molecules from the collision complex. Initial attack on a CO ligand is the main process as indicated by experiments with '*O'-and the ion/molecule reactions of the product ions resulting from the loss of three CO molecules with water, aliphatic alcohols, methanethiol and SO,. The attack on a CO ligand followed by loss of three CO molecules is suggested to yield C5H5MnO-ions with a (cyclopentadienone)MnH-structure in the reaction with CpMn(C0)3 and (methylcyclopentadienone)MnH-ions if CH$pMn(C0)3 is the substrate. A possible mechanism for the process leading to the indicated transformation of the Cp and CH,Cp ligands into C5H40 and CH&H30 ligands, respectively, is discussed together with the formation of (fulvene)Mn(OH)-ions following attack of O'-on CH$pMn(CO),. The (cyclopentadienone)MnH-and (methylcyclopentadienone)MnH-ions react with NzO by oxygen atom abstraction to form C5H5MnO; and C6H7MnO; ions, respectively.